Conventionally, there are known a technique in which a plurality of server units and a management unit are accommodated in a single housing, and the whole housing is operated as one server system. There is also known a technique in which a plurality of information storage units and a management unit are accommodated in a single housing, and the whole housing is operated as one information storage system. In this specification, such a server system and an information storage system are collectively referred to as an information system. In this information system, the management unit conducts the management to operate the information system as one integrated system in outward appearance.
Further, the management unit accesses the server units and the information storage units making up the information system to collect typical internal information such as fault information from these units. The internal information thus collected is used for the management to continue the operation of the information system smoothly in outward appearance, or accessed from outside the information system for maintenance of the information system.
This information system is generally connected to the internet or a LAN to conduct communication with many information terminals and personal computers. Through this communication, the information system carries out the job of providing the information and services to the information terminals, etc. and collecting the information from the information terminals and the personal computers. The housing of the information system also accommodates a communication unit (switch unit). The communication unit is in charge of communication to control the information flow between external devices and each unit in the system.
Once a fault develops in this communication system, the function of the information system is adversely affected. In many information systems, therefore, the redundancy of the communication path is secured by a plurality of communication units (switch units). In this connection, a technique has been proposed wherein in the case where a fault occurs in any of the plurality of the communication units making up the redundant structure, the internal information (especially, the fault information) of the communication unit that has developed the fault is sent to an external device through a communication unit free of the fault.